Never played with one. I've never tried to program a Z-Wave micro-controller either. The SDK is available now apparently without a NDA from silabs.com I think.
I'm not sure how far it will get you though. Typically in these types of devices there's some IC running everything and they are just talking I2C or SPI to the communications chip. Programming that IC would be the hurdle; getting the SDK for it primarily. They're just not released without a lot of paperwork and sometimes large fees. Every once in a while you get lucky and it's made with an ESP or something silly but not typically.
I'm not going to buy one to play around with it either way. The purchasing committee has said the 2020 budget is already mostly spent for HA toys and she wants me to lay low for a while on the home automation front. I have an entire bookcase shelf of devices new in the box that I don't have installed. If you decide to buy one and figure it out let us know how it goes.
